According to Wikipedia, "The bystander effect, or bystander indifference, is a social psychological theory stating that individuals are less likely to offer help to victims when other people are present."
Source from: https://en.wikipedia.org/wiki/Bystander_effect
Bystanders in cyberbullying refer to "individuals who witness cyberbullying".
Due to the specific nature of the online environment (e.g., openness, anonymity), there are a large number of potential viewers, i.e., bystanders, in cyberbullying situations. (Kowalski, Giumetti, Schroeder, & Lattanner, 2014)
Outsider
-Although they witnessed the bullying incident, they did nothing and condoned the bully's behavior.
Defender
-The protector will either directly oppose the bully's attempts to stop the bullying, or comfort and help the victim, or inform others with more power to intervene to end the bullying.
Reinforcer
-Reinforcers give encouragement or positive identification to the bully as a way to reinforce the bully's bullying behavior toward the victim.
Assister
-The assisters do not start the bullying, but they may be on the sidelines, fanning the flames or eventually joining the bullying.